Potamonautes, MACLEAY, 1838

Cumberlidge, Neil & Daniels, Savel R., 2022, A new multilocus phylogeny reveals overlooked diversity in African freshwater crabs (Brachyura: Potamoidea): a major revision with new higher taxa and genera, Zoological Journal of the Linnean Society 194 (4), pp. 1268-1311 : 1296-1298

GENUS POTAMONAUTES MACLEAY, 1838 S.S.

( FIGS 1B 3 [4], 6A–C, 10D; TABLES 1–3 )

Thelphusa A. Milne-Edwards, 1886: 149 ; 1887: 132, pl. 7: fig. 2, fig. 2a.

Potamon De Man, 1898: 436 ; Chace, 1942: 206.

Potamon (Potamonautes) Rathbun, 1900: 284 .

Potamon (Potamon) Rathbun, 1904: 296 , pl. 12: fig. 9; 1921: 419–422, pls 27, 28: fig. 1, fig. 10.

Potamonautes (Longipotamonautes) Bott, 1955: 244–245 , pl. VII: fig. 2a–d; figs 23, 73.

Potamonautes Balss, 1936: 174–177 , pls 9, 12, 13; Ng et al., 2008: 171; Cumberlidge, 2008: 72, 77, tab. 1; 2011: 79, 82–83 tabs 6.1, 6.3.

Potamonautes (Isopotamonautes) Bott, 1955 : not Potamonautes (Isopotamonautes) senegalensis = Occidensonautes senegalensis .

Potamonautes (Lirrangopotamonautes) Bo t t, 19 55, n o t Po ta m o n a u t es (Lirrangopotamonautes) adeleae = Potamonautes adeleae .

Potamonautes (Orthopotamonautes) Bott, 1955 for Potamonautes (Orthopotamonautes) depressus depressus and Potamonautes (Orthopotamonautes) sidneyi [not Potamonautes (Orthopotamonautes) depressus dybowskii = Lirrangopotamonautes dybowskii ].

Diagnosis: Cheliped carpus with two subequal large teeth. Third maxilliped ischium with vertical sulcus; thoracic sternal sulcus S3/4 deep, completely traversing sternum (or deep only at sides, faint in middle). G1 TA short (~1/4 to 1/3 as long as G1 SA; Fig. 6A–C ).

Type species: Thelphusa perlata H. Milne Edwards, 1837 , by original designation.

Species included: Potamonautes adeleae Bott, 1968 , Potamonautes anchietae (Brito-Capello, 1871) , Potamonautes barbarai Phiri & Daniels, 2014 , Potamonautes barnardi Phiri & Daniels, 2014 , Potamonautes bayonianus (Brito-Capello, 1864) , Potamonautes biballensis Bott, 1951 , Potamonautes brincki ( Bott, 1960) , Potamonautes clarus Gouws et al., 2000 , Potamonautes danielsi Peer et al., 2017 , Potamonautes dentatus Stewart et al., 1995 , Potamonautes depressus (Krauss, 1843) , Potamonautes dubius (Brito-Capello, 1873) , Potamonautes flavusjo Daniels et al., 2014 , Potamonautes gorongosa Cumberlidge et al., 2016 , Potamonautes granulatus Daniels et al., 1998 , Potamonautes isimangaliso Peer et al., 2015 , Potamonautes kensleyi Cumberlidge & Tavares, 2006 , Potamonautes lividus Gouws et al., 2001 , Potamonautes macrobrachii Bott, 1953 , Potamonautes mphlope Daniels, 2017 , Potamonautes mulanjeensis Daniels & Bayliss, 2012 , Potamonautes mutareensis Phiri & Daniels, 2013 , Potamonautes ngoyensis Daniels et al., 2019 , Potamonautes ntendekaensis Daniels et al., 2019 , Potamonautes parvicorpus Daniels et al., 2001 , Potamonautes parvispina Stewart, 1997 , Potamonautes perlatus (H. Milne Edwards, 1837) , Potamonautes principe Cumberlidge et al., 2002 , Potamonautes sidneyi ( Rathbun, 1904) , Potamonautes tuerkayi Wood & Daniels, 2016 , Potamonautes unispinus Stewart & Cook, 1998 , Potamonautes warreni (Calman, 1918) .

Distribution: This large genus is distributed throughout southern Africa, with the northern boundary in southern Tanzania (Ruvuma, Iringa, Mbeya provinces) and southern D.R. Congo (Kwanga and Katanga provinces). Eighteen species are endemic to South Africa: Po. barbarai , Po. barnardi , Po. brincki , Po. clarus , Po. danielsi , Po. dentatus , Po. flavusjo , Po. granularis , Po. isimangaliso , Po. lividus , Po. mphlope , Po. ngoyensis , Po. ntendekaensis , Po. parvicorpus , Po. parvispina , Po. perlatus , Po. tuerkayi and Po. warreni ( Bott, 1951; Stewart et al., 1995; Stewart, 1997a, b; Stewart & Cook, 1998; Daniels et al., 1998, 2001, 2002a, b, 2014, 2019, 2020; Gouws & Stewart, 2001; Gouws et al., 2000, 2001, 2015; Phiri & Daniels, 2013; Peer et al., 2015, 2017; Phiri & Daniels, 2013, 2014, 2016; Daniels, 2017; Wood & Daniels, 2016; Fig. 8D ). Five species are endemic to Angola: Po. adeleae , Po. anchietae , Po. biballensis , Po. kensleyi and Po. macrobrachii ( Cumberlidge & Tavares, 2006) and two species are endemic to Mozambique: Po. gorongosa and Po. mulanjeensis ( Daniels & Bayliss, 2012; Cumberlidge et al., 2016). In addition, Po. dubius ( Cumberlidge & Tavares, 2006) is endemic to Namibia, Po. mutareensis is endemic to Zimbabwe ( Phiri & Daniels, 2013), and Po. principe is endemic to Príncipe (Cumberlidge et al., 2002) . Additionally, four Potamonautes species have a widespread distribution: Po. bayonianus in the D.R. Congo, Angola, Namibia, Zimbabwe and Zambia ( Cumberlidge & Tavares, 2006), Po. unispinus in South Africa, Zimbabwe, Zambia and Botswana ( Stewart & Cook, 1998), Po. sidneyi in South Africa and Eswatini ( Gouws et al., 2000, 2001, 2015) and Po. depressus in South Africa and Lesotho ( Gouws et al., 2000, 2001).

Remarks: Potamonautes s.s. is revised here to accommodate 32 species from southern Africa. Bott (1955) established Po.( Potamonautes ) for Po. perlatus , Po. warreni , Po. bayonianus bayonianus and Po. bayonianus dubius . The first three of these taxa are grouped together with 24 other species from southern Africa in a well-supported lineage within the Potamonautini ( Fig. 1B 3 [4]; Daniels et al., 2006: fig 1; 2015: fig. 2; Daniels & Klaus, 2018: fig 1; Wood et al., 2019: fig 1). The name Potamonautes has been retained for this clade because it includes Thelphusa perlata H. Milne Edwards, 1837 , the type species of the genus. The freshwater crab fauna of southern Africa is the best studied on the continent, with DNA sequence data available for 31 species, the majority of which are from South Africa. Other parts of ther region are less well represented. For example, so far there are DNA data for only one species from Angola ( Po. anchietae ; Fig. 1B 3 [4]) and so the other five species from that country ( Po. adeleae , Po. biballensis , Po. dubius , Po. kensleyi and Po. macrobrachii ) are included in this revised genus based on morphological similarities ( Bott, 1955; Cumberlidge, 1999; Cumberlidge & Tavares, 2006).

Potamonautes s.s. includes several species that have previously been designated as the type species of a genus or subgenus, and so their status is reviewed below. For example, four species included here in Potamonautes s.s. were assigned by Bott (1955, 1960) to Po. (Isopotamonautes) Bott, 1955 as Po. (I.) anchietae , Po. (I.) macrobrachii , Po.(I.) senegalensis and Po. (I.) anchietae biballensis. Po. anchietae from Angola is however, the type species of Po. (Isopotamonautes) as Telphusa anchietae Brito Capello, 1871 , which now becomes a junior synonym of Potamonautes s.s. by priority because Thelphusa perlata H. Milne Edwards, 1837 , is the senior name. Furthermore, Bott’s (1955) subgenus Po. (Isopotamonautes) is paraphyletic and is not recognized here because it includes species from two separate lineages ( Fig. 1 ):all but one of whichremain in Potamonautes s.s., because Po. (I.)senegalensis from Senegal is phylogenetically distinct and is here assigned to the new genus Occidensonautes .

Bott (1968) included Po. adeleae in the subgenus Po. ( Lirrangopotamonautes ) Bott, 1955, but this species is here transferred to Potamonautes s.s. based on morphological characters. In addition, Bott (1960) included Po. brincki from South Africa in Gecarcinautes , but subsequent authors ( Stewart, 1997a; Cumberlidge, 1999; Cumberlidge & von Sternberg, 2002; Ng et al., 2008) treated Gecarcinautes as a junior synonym of Potamonautes and recognized Gecarcinautes brincki as a valid species. In the present work, Po. brincki is included in Potamonautes s.s. ( Fig. 1B 3 [4]).

Three taxa included here in Potamonautes s.s. were assigned by Bott (1955) to Po. (Orthopotamonautes) Bott, 1955 as Po. (O.) d. depressus , Po. (O.) d. dybowskii and Po. (O.) sidneyi . However, Po. depressus is the type species of Po. (Orthopotamonautes) as Thelphusa depressa Krauss, 1843 , and this becomes a junior synonym of Potamonautes s.s. because T. perlata H. Milne Edwards, 1837 is the senior synonym. The subgenus Potamonautes (Orthopotamonautes) is therefore paraphyletic and not recognized here because the taxa assigned to it by Bott (1955) belong to two different genetic lineages: Po. depressus is moved to Potamonautes s.s. ( Fig. 1B 3 [4]) and Po. dybowskii is moved to Lirrangopotamonautes ( Fig. 1B 3 [2]).

All but one of the species included here in Potamonautes s.s. shares the following characters. A distinct postfrontal crest that completely traverses the carapace between the epibranchial teeth, a small exorbital tooth, an epibranchial tooth that is reduced to a small granule, and the anterolateral margin of carapace behind the epibranchial tooth is either granulated or smooth. The exception is Po. warreni which has small teeth lining the anterolateral margin.

Figures

Figure 1. A, maximum clade credibility tree of the Afrotropical freshwater crab fauna based on four DNA loci with support values (posterior probabilities and bootstrap values of the ML analyses) with a geological timescale below the tree topology. Posterior probabilities> 0.95 pP (*above branch) and bootstrap values> 75% (* below branch) were regarded as statistically supported and are shown on the tree topology. Clade A, Liberonautinae, clade B, Potamonautinae, clade B1, Maritimonautini, clade B2, Erimetopini, clade B3, Potamonautini. B, detail of the maximum clade credibility tree of the Afrotropical freshwater crab fauna showing Clade B3 Potamonautini with the species included in the five genera within the tribe: Arcopotamonautes (B3[1]), Lirrangopotamonautes (B3[2]), Platythelphusa (B3[3]), Potamonautes s.s. (B3[4]) and Rotundopotamonautes (B3[5]).

Figure 3. Gonopods 1 and 2 of four genera in Liberonautinae. A–C, Buea asylos (Cumberlidge et al., 2019: fig. 7a, d; 8a); D–F, Potamonemus mambilorum (Cumberlidge et al., 2019: fig. 7b, e; 8b); G–I, Sudanonautes floweri; J–L, Louisea balssi (Mvogo Ndongo et al., 2018: fig. 5a–c, © Magnolia Press, reproduced with permission from the copyright holder). A, D, G, J, left G1 ventral view; B, E, H, K, left G1 dorsal view; C, F, I, L, left G2 ventral view. Scale bar: A, B, D, E, G, H, J, K = 2.0 mm, C, F, I, L = 1.8 mm.

Figure 6. Gonopods 1 and 2 of two genera in Potamonautini. A–C, Potamonautes anchetiae (CAW 450A), Angola. A, D, left G1 ventral view. D–F, Rotundopotamonautes loveni, Kenya, B, E, left G1 dorsal view; C, F, left G2 ventral view. Scale bar: A, B, D, E = 2.0 mm, C, F = 1.8 mm.

Figure 8. Maps showing the distributional ranges of (A) Potamonautinae, (B) Maritimonautini, (C) Erimetopini and (D) Potamonautini.